Video endoscopy is widely used in both diagnostic and interventional clinical applications. However, current video endoscopy systems do not support reconstruction and quantitative measurement of viewed anatomy. Yet, the ability to measure and model from video images has a number of potential clinical applications such as sizing a tumor, monitoring the change in size of a lesion over time, or computing area, size, or volume measurements of anatomy. At the same time, recent advances in algorithms for reconstruction from video images offer the opportunity of creating methods for quantitative endoscopic measurement (QEM) systems. The goal of the proposed project is to determine whether QEM is potentially usable as a routine diagnostic or interventional imaging modality. To do so, we intend to develop and evaluate a prototype system in the context of a specific, acute clinical need: the measurement of stenosis in pediatric airways. This is an ideal test application for QEM, as the current method of performing airway sizing is invasive, and it has a limited degree of accuracy. Furthermore, providing a new, more accurate modality would potentially enable better monitoring and treatment of this disease. The specific aims for this project are thus: 1. Aim 1: Develop a clinically deployable endoscopic data collection system. 2. Aim 2: Develop and validate algorithms for computing geometric properties of anatomic surfaces from a tracked video endoscope. 3. Aim 3: Demonstrate the feasibility of QEM in a controlled clinical setting. Finally, it is important to emphasize that, while we are focused on a specific clinical setting, the basic capabilities described here will have a much broader impact. Optical and video endoscopic devices are widely used in many areas of diagnosis and surgery. The ability to easily capture the full geometry of airways, sinus cavities, and so forth will open the door to a number of other scientific and clinical investigations. For example, it would become possible to perform repeat imaging to track the effect of treatment, and to perform in-office diagnostic procedures that currently rely on more expensive CT or MR imaging. Project Narrative: The proposed project will develop methods for computing accurate models of anatomy from endoscopic data. It will be specifically applied to a clinical problem of high relevant: the sizing of airway obstructions in young children. However, the possibility of performing simple, safe sizing of anatomic structures has wide relevant in many areas of medicine.